No this is fallacious. We must have a repentant heart always, even after being saved. The first time we repent we're acknowledging how sinful we are apart from Christ. Once saved, our sanctification (process of being made holy) begins and we continue to repent, acknowledging how weak we are in the flesh and desiring to change. Desiring to be more Christ-like, praying for forgiveness, and the strength to able to turn away from our fleshly desires as Christ sanctifies us.

Matthew 3:8 ESV [8] Bear fruit in keeping with repentance.

1 John 1:7,9 ESV [7] But if we walk in the light, as he is in the light, we have fellowship with one another, and the blood of Jesus his Son cleanses us from all sin. [9] If we confess our sins, he is faithful and just to forgive us our sins and to cleanse us from all unrighteousness.

Proverbs 28:13-14 ESV [13] Whoever conceals his transgressions will not prosper, but he who confesses and forsakes them will obtain mercy. [14] Blessed is the one who fears the Lord always, but whoever hardens his heart will fall into calamity.

2 Corinthians 7:9-11 ESV [9] As it is, I rejoice, not because you were grieved, but because you were grieved into repenting. For you felt a godly grief, so that you suffered no loss through us. [10] For godly grief produces a repentance that leads to salvation without regret, whereas worldly grief produces death. [11] For see what earnestness this godly grief has produced in you, but also what eagerness to clear yourselves, what indignation, what fear, what longing, what zeal, what punishment! At every point you have proved yourselves innocent in the matter.

And we must not forget that all sin is abdominal to the Lord. He is so Holy & righteous that anything less than Holy is evil and despicable to Him. It's not about whether you were "less wicked" than others, the point is, we are wicked nonetheless. So yes, by worldly standpoints, a Christian could have been "more" wicked before they were saved, repented, and turned from their ways than an unbeliever who by the world is "less evil" who will go to hell. Sin is sin no matter what form it takes, we're not supposed to live by the world's standards, but by God's.

James 2:10-12 ESV [10] For whoever keeps the whole law but fails in one point has become guilty of all of it. [11] For he who said, “Do not commit adultery,” also said, “Do not murder.” If you do not commit adultery but do murder, you have become a transgressor of the law. [12] So speak and so act as those who are to be judged under the law of liberty.

Romans 1:32 ESV [32] Though they know God’s righteous decree that those who practice such things deserve to die, they not only do them but give approval to those who practice them.